1. Technical Field
The present disclosure relates generally to integrated circuit semiconductor devices. In particular, the present disclosure relates to reversible electronic fuse and antifuse structures for semiconductor devices.
2. Description of Related Art
The proliferation of electronics in our modern world is in large part due to integrated circuit semiconductor devices. Integrated semiconductor devices are designed and used in widely differing applications and there are currently numerous schemes for providing integrated circuit interconnections well known in the art, for example, electrically programmable interconnections for use in integrated circuits. Electrically programmable interconnect schemes include fuses and antifuse devices. Fuses are reprogrammable interconnect, which may be altered by a user after initial circuit configuration has been accomplished. Antifuses are one-time programmable, that is, it cannot be reconfigured once initially configured. Fuse and antifuses are widely used in field programmable devices for repairing defective circuitry.
One type of fuse device includes an ohmic element which has a low electrical resistance by default. This type of use may include metal lines such as copper, tungsten or aluminum. When programmed, the electrical resistance will increase significantly and an electrically open condition is achieved. Programming is usually done by a high energy laser during which the fuse material is ablated away. Laser ablation is typically used because it is relatively simple, thus permitting for less complicated design of the fuse element. However, because the laser beam is relatively large, this technique requires enough clearance between the fuse element and the rest of the circuitry to avoid collateral damage.
Another type of fuse device includes an electrically programmable fuse element. These fuses may include poly-silicide having polycrystalline silicon and an overlayer of silicide.
During programming, a high electrical current is passed through the electronic fuse element resulting in the fuse element being heated to a very high temperature. Thus the fuse material is obliterated creating an electrically open state. Yet another type of electronic fuse is one formed on a diode. However, instead of passing a high current as in the previous case, a high voltage is used to break down the semiconductor during programming. Yet another type of electronic fuses is based on electromigration. Current crowding takes place around a fixed location thus initiating electromigration which results in further current crowing and material migration along the direction of the electron movement along the fuse element.
A major advantage of electronic fuse over laser fuse is that the fuse element can be made very small and spacing between the fuse element and the neighboring circuit element can be significantly smaller. However, the design of an electronic fuse is more complicated, particularly in the choice of the material and the integration scheme employed. For example, U.S. Pat. No. 5,973,977 describes an electronic fuse-antifuse structure having a horizontal B-fuse portion and a vertical A-fuse portion disposed between two metallization layers of an integrated circuit device.
An antifuse device includes an antifuse element that is typically electrically non-conductive, i.e. at very high ohmic resistance. When programmed, the electrical resistance of the antifuse decreases significantly. Commonly used antifuse material includes very thin layer of silicon oxide, amorphous silicon. In addition, U.S. Pat. No. 5,610,084 discloses a technique to make very thin (e.g. 5 nm) silicon oxide, by implanting nitrogen into a silicon layer for slowing down the rate of oxidation of the silicon layer.
U.S. Pat. No. 5,794,094 discloses an antifuse structure consisting of a thin layer of amorphous silicon sandwiched in between two metal electrodes. During programming, an electrical voltage is applied across the electrode to induce metal atoms diffuse into the silicon layer leading to a resistance drop from about 20 to 100 ohms.
U.S. Pat. No. 6,344,373 B1 describes yet another antifuse structure wherein the antifuse element consists of a layer of injector layer such as a two phase material (e.g. silicon rich nitride or silicon rich oxide) and a dielectric layer. Initially, the two layers are non-conducting but when a sufficient voltage is applied across the two layers, they will fuse together and become conducting.
Furthermore, some devices incorporate both fuse and antifuse. For example, U.S. Pat. No. 5,903,041 describes a two terminal fuse-antifuse structure having an air-gap. The air-gap provides a space for the disrupted fuse material, thus reducing the physical stress.
Accordingly, a need exist for an apparatus and simplified method of forming electronic fuse and antifuse elements by increasing the current density. These apparatus and methods are desirable for the electrical fuse technology to minimize energy consumption and the cost of programming.